Control method and control apparatus of inverter

Abstract

To provide a control method and a control apparatus of an inverter, of which a power conversion efficiently is improved while protecting a power module.SOLUTION: The present invention provides a control method of an inverter for driving a motor with a power module. The control method includes the steps of: predicting temperature of the power module; detecting a voltage of a battery for supplying power to the motor; and calculating a command value of a current supplied to the inverter or detecting an output current of the power module. Then, a gate resistance of the power module is set to any one of a first value or a second value of which the resistance value is lower than that of the first value on the basis of the temperature of the power module, the voltage of the battery, and the command value of the current or the output current of the power module.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method and a control device for an inverter. [Background technology]

[0002] Generally, the lower the temperature, the lower the withstand voltage of the power module (driving semiconductor element) in the inverter of an electric vehicle. Conventionally, a technology is known that protects the power module by switching the gate resistance of the power module to a high value at low temperatures to suppress surge voltage so that the withstand voltage of the power module is not exceeded.

[0003] Patent Document 1 discloses a power converter (inverter) that sets the gate resistance of a switching element of a power semiconductor based on the temperature of the power semiconductor. In this power converter (inverter), the gate resistance is also set to a high value when the switching element is at a low temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2022 / 044298 A1 Summary of the Invention [Problem to be solved by the invention]

[0005] In the power converter (inverter) described in Patent Document 1, the gate resistance is increased at low temperatures, which increases loss accordingly, and this may reduce the power conversion efficiency of the inverter.

[0006] The present invention has been made in consideration of the above problems, and has an object to provide a control method and control device for an inverter that improves power conversion efficiency while protecting a power module. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a method for controlling an inverter for driving a motor having a power module. The method includes predicting a temperature of the power module, detecting a voltage of a battery that supplies power to the motor, and calculating a command value for a current supplied to the inverter or detecting an output current of the power module. Then, based on the temperature of the power module, the voltage of the battery, and the command value for the current or the output current of the power module, the method sets a gate resistance of the power module to either a first value or a second value having a resistance value lower than the first value. Effect of the Invention

[0008] According to the present invention, the gate resistance is set based not only on the temperature of the power module, but also on the voltage of the battery and the current command value or the output current of the power module. Therefore, it is possible to set the gate resistance to a low resistance within a range that does not exceed the withstand voltage of the power module. Therefore, it is possible to suppress losses while protecting the power module. In other words, it is possible to improve the power conversion efficiency of the inverter while protecting the power module. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram of a motor control system to which an inverter control method according to an embodiment of the present invention is applied. [Diagram 2] FIG. 2 is a diagram showing a detailed configuration of the drive circuit. [Diagram 3] FIG. 3 is a diagram showing a method for selecting a gate resistance. [Figure 4] FIG. 4 is a diagram showing the range of change in the motor rotation speed within a calculation period. [Diagram 5] FIG. 5 is a diagram showing the relationship between the motor torque and the maximum current increase value. [Figure 6] FIG. 6 is a diagram showing the range of the motor rotation speed that can increase within a calculation period. [Figure 7] FIG. 7 is a flowchart of the gate resistance setting process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] [Embodiment] Fig. 1 is a schematic diagram of a motor control system 100 to which an inverter control method according to the present embodiment is applied. As shown in Fig. 1, the motor control system 100 is mainly composed of a battery 1 as a DC power source, an inverter 2 for driving a motor, a motor 3 configured as, for example, a three-phase AC motor, and a controller 10. In this embodiment, the motor control system 100 including the inverter 2 is mounted on a vehicle such as an electric vehicle, but is not necessarily limited to this.

[0012] The battery 1 is a high-power battery that supplies driving power to a motor (driving motor) 3 via an inverter 2. The motor 3 is driven to rotate by the power supplied from the battery 1, and if the motor 3 is an in-vehicle motor, the vehicle runs by the power of the motor 3. The motor control system 100 includes a voltage sensor (means for detecting the voltage of the battery 1) 11 that detects the voltage between the terminals of the battery 1, and the battery voltage V detected by the voltage sensor 11 is b is transmitted to the controller 10.

[0013] The inverter 2 is a power converter that adjusts the power supplied from the battery 1 to the motor 3 (or the regenerative power from the motor 3 to the battery 1), and performs power conversion from DC to three-phase AC or from three-phase AC to DC between the battery 1 and the motor 3.

[0014] The inverter 2 has a smoothing capacitor 21 that suppresses ripples, a power module 22 consisting of a plurality of (six in the figure) power semiconductor element units 220 that constitute a switching circuit, a drive circuit 23 that drives the power semiconductor element units 220, and a cooler 24. The operation of the inverter 2 is controlled by a controller 10.

[0015] The power semiconductor element unit 220 is composed of three-phase six arms, i.e., upper arms UP, VP, WP and lower arms UN, VN, WN in each of the three phases UVW, and includes voltage-controlled switching elements 221 composed of semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors), and freewheel diodes 222 that pass freewheel current from the motor 3 when each switching element 221 is off.

[0016] The drive circuit 23 is connected in parallel to each switching element 221. The drive circuit 23 drives (turns on and off) each switching element 221 based on a PWM (Pulse Width Modulation) signal input from the controller 10. Through this switching operation, when the motor 3 is in power running, the DC power from the battery 1 is converted into desired AC power and supplied to the motor 3. On the other hand, when the motor 3 is in regeneration, the rotational energy of the motor 3 is converted into DC power and supplied to the battery 1. The drive circuit 23 also drives (turns on and off) each switching element 221 based on a PWM (Pulse Width Modulation) signal input from the controller 10. sw With reference to the above, the gate resistance R of the switching element 221 g Set the gate resistance R g The method of setting will be described in detail later.

[0017] The cooler 24 cools the power module 22. The cooler 24 is, for example, configured with a water jacket for supplying cooling water to the power semiconductor element section 220 for cooling. w The cooling water temperature T detected by the cooling water temperature sensor 25 is provided. w is transmitted to the controller 10.

[0018] The controller 10 is configured by a computer equipped with a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface) and programmed to execute each process described below. The controller 10 can also be configured by multiple computer hardware that executes each process in a distributed manner.

[0019] The controller 10 controls the operation of the inverter 2. Specifically, the controller 10 receives the required torque of the motor 3, which is an electric load, and generates a PWM signal for defining the switching pattern (duty ratio) of each switching element 221. More specifically, the controller 10 determines a current command value (a command value for a current supplied to the inverter 2) I that realizes a desired required torque according to an external required load (such as the amount of operation of an accelerator pedal in the case of a vehicle). a and calculates the current command value I a The control circuit 10 calculates a control voltage (voltage command value) that will make the deviation between the actual current of the motor 3 and the input voltage zero, and generates a PWM signal to realize the calculated voltage command value.

[0020] In addition, the controller 10 controls the gate resistance R g Specifically, the controller 10 predicts the temperature of the power module 22 and sets the voltage V of the battery 1. b , current command value I a , and the predicted temperature of the power module 22, the controller 10 determines the switching speed of the switching element 221, and generates a control signal for realizing the determined switching speed. More specifically, the controller 10 generates a speed switching signal S sw As described above, the drive circuit 23 generates the speed switching signal S sw With reference to the above, the gate resistance R of the switching element 221 gThat is, the controller 10 sets the voltage V of the battery 1. b , current command value I a , and the temperature of the power module 22, the gate resistance R of the switching element 221 is controlled via the drive circuit 23. g The controller 10 sets the cooling water temperature T w is predicted as the temperature of the power module 22. The gate resistance setting process will be described in detail later.

[0021] As described above, the operation of the inverter 2 is controlled by the controller 10. In this embodiment, the controller 10 controls the operation of the inverter 2, and the battery voltage V b and cooling water temperature T w The voltage sensor 11 for detecting this and the cooling water temperature sensor 25 constitute an inverter control device.

[0022] Fig. 2 is a diagram showing a detailed configuration of the drive circuit 23. For simplification, Fig. 2 shows only a connection portion between the drive circuit 23 and one power semiconductor element unit 220. However, in this embodiment, all of the power semiconductor element units 220 are connected to the drive circuit 23 in the manner shown in Fig. 2.

[0023] The controller 10 receives the battery voltage V from the voltage sensor 11. b , the coolant temperature T from the coolant temperature sensor 25 w The controller 10 receives the cooling water temperature T w is predicted as the temperature of the power module 22. Then, the controller 10 predicts the battery voltage V b , the temperature of the power module 22 (cooling water temperature T w ), and the calculated current command value I a to speed change signal S sw and generates the speed switching signal S sw is output to the gate drive IC 23a.

[0024] The gate driver IC 23a of the driver circuit 23 receives the speed switching signal S swis used as an input, and the gate resistance R of the switching element 221 g More specifically, the gate driver IC 23a sets the speed switching signal S sw With reference to the above, the gate resistance R of the switching element 221 g , the relatively high first gate resistance R g1 (first value) and a relatively low second gate resistance R g2 (second value) and where the gate resistor R g The first gate resistor R g1 On the other hand, when the gate resistance R g The second gate resistor R g2 , the switching speed becomes relatively high. g The larger the gate resistance R of the switching element 221 is set, the smaller the gate current that charges and discharges the capacitance of the switching element 221 becomes, and the slower the switching speed becomes. g The smaller the gate resistance R of the switching element 221 is set, the larger the gate current becomes, and the higher the switching speed becomes. g The first gate resistance R is relatively high. g1 The state where the gate resistor R g Second gate resistance R g2 The state where the control mode is set to the high-speed mode corresponds to the state where the control mode is set to the high-speed mode. Furthermore, as can be seen from FIG. 2, the gate driving IC 23a provides the same gate resistance R g Therefore, the gate driving IC 23a simultaneously sets the first gate resistance R g1 or the second gate resistor R g2 That is, the gate driving IC 23a drives all the power semiconductor element units 220 so that the switching speeds of the power semiconductor element units 220 are simultaneously switched between low speed and high speed.

[0025] Therefore, in the inverter control method of this embodiment, the switching speeds of all the power semiconductor element units 220 are adjusted collectively by one drive circuit 23. That is, the gate resistance of the entire power module 22 is set by the drive circuit 23. Therefore, it is possible to adjust all of these switching speeds (gate resistances) without providing a drive circuit for each power semiconductor element unit 220. This simplifies the circuit configuration and prevents the entire device from becoming large.

[0026] In this way, the drive circuit 23 controls the battery voltage V b , cooling water temperature T w , and the calculated current command value I a The speed switching signal S generated by the controller 10 based on sw With reference to the gate resistance R g Set.

[0027] Incidentally, it is known that the withstand voltage of a power module (power semiconductor element) in an inverter for an electric vehicle generally tends to have a positive slope with respect to temperature. Therefore, when the power module is at a high temperature, the gate resistance of the power module (semiconductor switching element) can be lowered and the switching speed can be made relatively fast. Increasing the switching speed reduces the loss due to switching and improves the power conversion efficiency of the inverter.

[0028] On the other hand, when the temperature of the power module is low, if the gate resistance of the power module (semiconductor switching element) is reduced and the switching speed is increased, a switching surge is likely to occur. For this reason, when the temperature of the power module is low, it is possible to increase the gate resistance and slow down the switching speed to protect the power module so that the voltage of the power module (power semiconductor element) does not exceed the withstand voltage due to the surge voltage. However, if the gate resistance is increased when the power module is low, the loss due to switching increases accordingly. Here, if the gate resistance is set based only on the temperature of the power module, for example, the gate resistance may be set high even when there is actually a margin up to the withstand voltage of the power module (power semiconductor element). In other words, even when there is no risk of exceeding the withstand voltage of the power module, the gate resistance is set high, and there is a risk of the power conversion efficiency of the inverter being reduced.

[0029] In contrast, in the inverter control method of the present embodiment, not only the temperature of the power module 22 but also the voltage V b , and the current command value I a Based on the gate resistance R g Therefore, even if the power module 22 is at a low temperature, the voltage V b and the current command value I a Depending on the case, the second gate resistor R may have a low resistance within a range not exceeding the withstand voltage of the power module 22. g2 Therefore, it is possible to suppress loss while protecting the power module 22. That is, it is possible to improve the power conversion efficiency of the inverter 2 while protecting the power module 22.

[0030] The method of selecting the gate resistance (gate resistance setting process) will be described in detail below.

[0031] FIG. 3 shows the gate resistance R g As described above, the controller 10 selects the cooling water temperature T wis predicted as the temperature of the power module 22. The withstand voltage characteristics of the power module 22 change depending on the ambient temperature, but the temperature of the power module 22 itself may vary depending on the monitoring position due to the influence of the self-heating of the inverter 2 and the motor 3. In contrast, the cooling water temperature T w is closer to the ambient temperature of the power module 22. w By using this, it is possible to more accurately predict the ambient temperature of the power module 22. In this embodiment, the temperature of the power module 22 refers to the ambient temperature of the power module 22 (the outside air temperature on the surface).

[0032] As shown in Figure 3, the cooling water temperature T w is a given value (temperature threshold) T th In this case, the switching speed is set to high-speed mode and the gate resistor R g is the low resistance second gate resistor R g2 (In FIG. 3, it is represented as Lo. The same applies below.) This reduces the loss due to switching and improves the power conversion efficiency of the inverter 2. Note that the temperature threshold T th is the gate resistance R g The second gate resistor R g2 , the temperature threshold T is set to a value that does not exceed the withstand voltage of the power module 22, and can be determined in advance by experiments, etc. th is set to 25°C.

[0033] In addition, the cooling water temperature T w is the temperature threshold T th Even if the voltage of battery 1 is less than V b is a given voltage value (voltage threshold) V th If the switching speed is set to fast mode, the gate resistor R g is the low resistance second gate resistor R g2 That is, the voltage V of battery 1 is set to b is sensitive to the voltage of the power module 22 and the voltage V of the battery 1 bHowever, if the cooling water temperature T w is the temperature threshold T th Even if the gate resistance R g is the low-resistance second gate resistor R g2 As a result, even if the power module 22 is at a low temperature, the gate resistance R g is a low-resistance second gate resistor R within a range not exceeding the withstand voltage of the power module 22. g2 Therefore, it is possible to reduce the loss due to switching while protecting the power module 22, and improve the power conversion efficiency of the inverter 2. From the above viewpoint, the voltage threshold V th is the gate resistance R g The second gate resistor R g2 , the voltage threshold V is set to a value that does not exceed the withstand voltage of the power module 22, and can be determined in advance by experiments or the like. For example, th is set to a voltage value of the battery 1 that does not exceed the withstand voltage of the power module 22 even at the peak of the phase of the current flowing through the inverter 2.

[0034] In addition, the cooling water temperature T w is the temperature threshold T th and the voltage of battery 1 is V b is the voltage threshold V th Even in the above case, the command value I of the current supplied to the inverter 2 a is a predetermined value (current threshold) I aa If the switching speed is set to fast mode, the gate resistor R g is the low-resistance second gate resistor R g2 That is, when the value of the current flowing through the inverter 2 is sufficiently low, even if the temperature of the power module 22 is low, there is no risk of exceeding the withstand voltage of the power module 22. Therefore, the current command value I a However, if the cooling water temperature T w is the temperature threshold T th Even if the gate resistance R g is the low-resistance second gate resistor R g2As a result, when the power module 22 is at a low temperature and the voltage V b is the voltage threshold V th Even in the above cases, the gate resistance R g is a low-resistance second gate resistor R within a range not exceeding the withstand voltage of the power module 22. g2 Therefore, it is possible to further reduce the loss due to switching while protecting the power module 22, and to further improve the power conversion efficiency of the inverter 2. From the above viewpoint, the current threshold I aa is the gate resistance R g The second gate resistor R g2 , the current threshold I is set to a value that does not exceed the withstand voltage of the power module 22, and can be determined in advance by experiments, etc. aa is set to a current value that does not exceed the withstand voltage of the power module 22 even at the peak of the phase of the current flowing through the inverter 2.

[0035] In contrast, the cooling water temperature T w is the temperature threshold T th and the voltage of battery 1 is V b is the voltage threshold V th The above is true, and the command value I a is the current threshold I aa In this case, the switching speed is set to slow mode and the gate resistor R g is the high resistance first gate resistor R g1 (Indicated as Hi in FIG. 3.) This suppresses the surge voltage, prevents the voltage of the power module 22 from exceeding the withstand voltage, and reliably protects the power module 22.

[0036] In addition, in the initial setting at the start of inverter 2, the gate resistance R g is always the first gate resistor R g1 Normally, the power module has a small thermal time constant and is quickly cooled, so that the power module 22 is in a low temperature state when the inverter 2 is started. Therefore, at the start-up, the first gate resistor R g1By applying the above, the power module 22 (switching element 221) is protected from surge voltage, and the temperature of the power module 22 (cooling water temperature T w ), the voltage of battery 1 V b , and the current command value I a Based on the gate resistance R g Set.

[0037] As described above, in this embodiment, the cooling water temperature T w is the temperature threshold T th and the voltage of battery 1 is V b is the voltage threshold V th In this case, the current command value I a is the current threshold I aa Whether or not the gate resistance R g However, it is preferable to select the high or low current command value I a , the current command value I a The maximum current that can increase within a calculation period (maximum current increase) ΔI max The value I added max (That is, I a +ΔI max ) is the current threshold I aa Whether or not the gate resistance R g Select high or low.

[0038] That is, in the motor control, the control (calculation) period depends on, for example, the communication period of the in-vehicle communication network, and calculation cannot be performed for a period shorter than the communication period. a is calculated at a predetermined calculation period (for example, 10 ms). w Based only on the gate resistance R g When selecting high or low, the time constant is long, so the cooling water temperature T w There is no significant change in the gate resistance R g The second gate resistor R g2 After setting, the cooling water temperature T wThere is almost no risk that the current command value I fluctuates and exceeds the withstand voltage of the power module 22. On the other hand, the current value flowing through the inverter 2 (hereinafter also referred to as the current value of the inverter 2) varies depending on the fluctuation of the motor rotation speed N within a predetermined calculation period. a For example, as shown in FIG. 4, when the motor torque Tq is Tq0 and the motor rotation speed N is N0, the motor rotation speed N can increase to N1 within a predetermined calculation period. When the motor rotation speed N increases, the value of the current flowing through the inverter 2 increases. Therefore, the current command value I a When judging (calculating), the current command value I a is the current threshold I aa Even if the motor rotation speed N is less than the threshold value I aa In particular, if the motor speed changes to a high speed within the calculation cycle, the power (output) increases, and there is a risk of a high current flowing unintentionally. In such a case, the gate resistance R g is the low-resistance second gate resistor R g2 Therefore, there is a risk that the withstand voltage of the power module 22 may be exceeded due to an increase in the current value. w is the temperature threshold T th and the voltage of battery 1 is V b is the voltage threshold V th In the above cases, the torque Tq of the motor 3 and the maximum current increase ΔI max Refer to the map showing the relationship between the maximum current increase ΔI max and calculate the current command value I a Maximum current increase ΔI max The value I added max is the current threshold I aa Whether or not the gate resistance R g It is preferable to select a high or low value. This can reliably prevent the withstand voltage of the power module 22 from being exceeded. For example, when the motor torque Tq is Tq0, as shown in FIG. max becomes ΔI1, and the current command value I a is the current threshold I aa Even if the current command value Ia The current threshold I aa In this case, the gate resistance R g is the high resistance first gate resistor R g1 In addition, the torque Tq of the motor 3 in FIG. 5 and the maximum current increase ΔI max The map showing the relationship can be created in advance through experiments or the like.

[0039] More preferably, the maximum change in the rotation speed N of the motor 3 within a predetermined calculation period is predicted based on the acceleration resistance of the vehicle in which the inverter 2 is mounted, and the current value of the inverter 2 that increases due to the predicted maximum change in the rotation speed N of the motor 3 is set as a maximum current increase ΔI max The maximum change in the rotation speed N of the motor 3 can be predicted by the following calculation procedure.

[0040] First, the acceleration resistance can be calculated by the following formula (1).

number

[0041] The driving force, gradient resistance, air resistance, and rolling resistance can be calculated using the following formulas (2) to (5).

number

number

number

number

[0042] Next, the vehicle acceleration is calculated using the calculated acceleration resistance according to the following equation (6), and the vehicle speed is calculated according to the following equation (7).

number

number

[0043] The maximum change in the rotation speed N of the motor 3 (fluctuation in the motor rotation speed) can be calculated (predicted) by the following formula (8) using the calculated vehicle speed. Then, using a map or the like, the current value of the inverter 2 that increases due to the predicted maximum change in the rotation speed N of the motor 3 is predicted, and this is called the maximum current increase ΔI max Let us assume that.

number

[0044] In this way, the maximum change in the rotation speed N of the motor 3 is predicted based on the acceleration resistance of the vehicle, and the current value of the inverter 2 that increases due to the predicted maximum change in the rotation speed N of the motor 3 is set as the maximum current increase ΔI max By doing so, the gate resistance R g The second gate resistor R g2 For example, as shown in FIG. 6, when the motor torque Tq is Tq0 and the motor rotation speed N is N0, the motor rotation speed N that can be increased within a predetermined calculation period can be predicted to be N2, which is smaller than N1, by taking into account the acceleration resistance of the vehicle. Therefore, the maximum current increase ΔI max is smaller than ΔI1 calculated from only the motor torque Tq. max Compared to the case where the second gate resistor R g2 In other words, the maximum change in the number of rotations N of the motor 3 is predicted based on the acceleration resistance, and the maximum current increase ΔI max By determining this, the switching loss can be further suppressed and the power conversion efficiency of the inverter 2 can be further improved.

[0045] Also, preferably, the cooling water temperature T w, the voltage of battery 1 V b , and the current command value I a are the thresholds T th , V th , I aa When determining whether the cooling water temperature T w , the voltage of battery 1 V b , and the current command value I a Hysteresis is set for each of these to prevent false detection and chattering. Also, the voltage V of battery 1 b When setting the hysteresis, the hysteresis threshold should be set to be equal to or greater than the maximum voltage fluctuation that can occur at the maximum power input / output of battery 1, or set to be equal to or greater than the voltage V b is the voltage threshold V th Before determining whether the voltage is greater than or equal to the voltage threshold V th The maximum voltage fluctuation that can occur at

[0046] 7 is a flowchart of the gate resistance setting process. The following process is repeatedly executed by the controller 10 at a predetermined calculation cycle.

[0047] When the inverter 2 is started, for example, by turning on the ignition switch of the vehicle, the controller 10 starts the gate resistance setting process.

[0048] When the gate resistance setting process is started, in step S101, the controller 10 sets the switching speed to a low-speed mode as an initial setting at the start of the inverter 2, thereby setting the gate resistance R g The first gate resistor R g1 Set to.

[0049] The process of step S101 is executed only when the inverter 2 is started up, and in the second and subsequent calculation cycles, the process of step S101 is not executed, but the processes of step S102 and subsequent steps are executed.

[0050] In step S102, the controller 10 detects the cooling water temperature T w is the temperature threshold Tth It is judged whether the cooling water temperature T w is the temperature threshold T th If the withstand voltage of the power module 22 is high, the controller 10 sets the switching speed to the high-speed mode in step S103 to reduce the gate resistance R g The second gate resistor R g2 This reduces switching losses.

[0051] After executing the process of step S103, the controller 10 ends the gate resistance setting process.

[0052] On the other hand, in step S102, the cooling water temperature T w is the temperature threshold T th If it is less than this, the controller 10 executes the process of step S112.

[0053] In step S112, the controller 10 detects the voltage V b is the voltage threshold V th Determine whether the voltage of battery 1 is less than V b is the voltage threshold V th If it is less than the voltage V of the battery 1, the controller 10 executes the process of step S103. b is the voltage threshold V th If the voltage Vcc is less than 1 V, there is no risk of exceeding the withstand voltage of the power module 22, so in step S103, the controller 10 sets the switching speed to the high-speed mode and reduces the gate resistance R g The second gate resistor R g2 This reduces switching losses.

[0054] After executing the process of step S103, the controller 10 ends the gate resistance setting process.

[0055] On the other hand, in step S112, the voltage V of the battery 1 b is the voltage threshold V thIf so, the controller 10 executes the process of step S122.

[0056] In step S122, the controller 10 calculates the current command value I a is the current threshold I aa It is judged whether the current command value I a is the current threshold I aa If it is less than the current command value I a is the current threshold I aa If the voltage Vcc is less than 1 V, there is no risk of exceeding the withstand voltage of the power module 22, so in step S103, the controller 10 sets the switching speed to the high-speed mode and reduces the gate resistance R g The second gate resistor R g2 This reduces switching losses.

[0057] After executing the process of step S103, the controller 10 ends the gate resistance setting process.

[0058] On the other hand, in step S122, the current command value I a is the current threshold I aa If so, the controller 10 executes the process of step S104.

[0059] In step S104, the controller 10 sets the switching speed to a low-speed mode, thereby reducing the gate resistance R g The first gate resistor R g1 This suppresses surge voltage, prevents the voltage of the power module 22 from exceeding the withstand voltage, and protects the power module 22.

[0060] In step S122, the current command value I a is the current threshold I aa However, as described above, it is preferable to determine whether the current command value I a Instead, the current command value I a Maximum current increase ΔI maxThe value I added max is the current threshold I aa In this case, the current command value I a Maximum current increase ΔI max The value I added max is the current threshold I aa If it is less than 1, the controller 10 executes the process of step S103 and increases the gate resistance R g The second gate resistor R g2 On the other hand, the current command value I a Maximum current increase ΔI max The value I added max is the current threshold I aa If so, the controller 10 executes the process of step S104 to increase the gate resistance R g The first gate resistor R g1 Set to.

[0061] According to the above-described inverter control method of the present embodiment, the following effects can be obtained.

[0062] According to the inverter control method of the present embodiment, the temperature of the power module 22 and the voltage V b and the current command value I a Based on this, the gate resistance R of the power module 22 is g The first gate resistor R g1 (first value), or the first gate resistor R g1 A second gate resistor R with a lower resistance than (the first value) g2 In this way, not only the temperature of the power module 22 but also the voltage V b , and the current command value I a Based on the gate resistance R g Therefore, even if the power module 22 is at a low temperature, the voltage V b and the current command value I a Depending on the case, a low resistance second gate resistor R may be used as long as it does not exceed the withstand voltage of the power module. g2Therefore, it is possible to suppress loss while protecting the power module 22. That is, it is possible to improve the power conversion efficiency of the inverter 2 while protecting the power module 22.

[0063] According to the inverter control method of the present embodiment, the cooling water temperature T w is predicted as the temperature of the power module 22. In this way, the cooling water temperature T w By using this, the ambient temperature of the power module 22 can be predicted more accurately.

[0064] According to the inverter control method of the present embodiment, the cooling water temperature T w is the temperature threshold (predetermined value) T th Less than or equal to the voltage of battery 1 V b is the voltage threshold (predetermined voltage value) V th If less than 1000 V, the gate resistance R g The second gate resistor R g2 (second value). In this way, the cooling water temperature T w is the temperature threshold (predetermined value) T th Even if the voltage of battery 1 is less than V b is the voltage threshold (predetermined voltage value) V th If less than 100, the gate resistance R g is the low-resistance second gate resistor R g2 As a result, even if the power module 22 is at a low temperature, the gate resistance R g is the low resistance second gate resistor R g2 Since the switching loss is set to (the second value), the power module 22 can be protected while reducing the switching loss, thereby improving the power conversion efficiency of the inverter 2.

[0065] According to the inverter control method of the present embodiment, the cooling water temperature T w is the temperature threshold (predetermined value) T th Less than or equal to the voltage of battery 1 Vb is the voltage threshold (predetermined voltage value) V th And the current command value I a is the current threshold (predetermined value) I aa If less than 1000 V, the gate resistance R g The second gate resistor R g2 (second value). In this way, the cooling water temperature T w is the temperature threshold (predetermined value) T th Less than or equal to the voltage of battery 1 V b is the voltage threshold (predetermined voltage value) V th Even in the above cases, the command value I of the current supplied to the inverter 2 a is the current threshold (predetermined value) I aa If less than this, the gate resistance R g is the low resistance second gate resistor R g2 (second value). As a result, when the power module 22 is at a low temperature and the voltage V b is the voltage threshold (predetermined voltage value) V th Even if the gate resistance R g is the low resistance second gate resistor R g2 (second value). Therefore, while protecting the power module 22, the loss due to switching can be further reduced, and the power conversion efficiency of the inverter 2 can be further improved.

[0066] According to the inverter control method of the present embodiment, when the inverter 2 is started, the gate resistance R g The first gate resistor R g1 (first value). This makes it possible to protect the power module 22 (switching element 221) from a surge voltage when the inverter 2 is started up and the power module 22 is in a low temperature state.

[0067] In this embodiment, a controller 10 controls the operation of the inverter 2, and a battery voltage V b and cooling water temperature T wIn the above embodiment, the inverter control device is configured by the voltage sensor 11 and the cooling water temperature sensor 25 that detect the temperature of the power module 22, but this is not necessarily limited to this. b and a means for detecting a command value I a The specific configuration of each means is not limited to the above as long as the controller 10 includes a means for calculating the current command value I a However, this is not necessarily limited to this, and the current command value I a Alternatively, the current command value I may be calculated by a controller higher than the controller 10 and transmitted to the controller 10. In this case, the higher-level controller may calculate the current command value I a This provides a means of calculating

[0068] In this embodiment, the cooling water temperature T w is the temperature threshold T th and the voltage of battery 1 is V b is the voltage threshold V th In this case, the current command value I a , or the current command value I a Maximum current increase ΔI max The value I added max is the current threshold I aa Whether or not the gate resistance R g However, this is not necessarily limited to the above. w is the temperature threshold T th and the voltage of battery 1 is V b is the voltage threshold V th In the above case, the output current I c is a given current threshold I cc Whether or not the gate resistance R g In this case, the output current I cAs a means for detecting the temperature of the power module 22, for example, a current sensor for detecting the output current of one of the power semiconductor element units 220 is used. In this case, a means for detecting the temperature of the power module 22 (coolant temperature sensor 25) and a voltage V of the battery 1 are also used. b and a means for detecting the output current I of the power module 22. c The inverter control device is configured by a means for detecting the cooling water temperature T w is the temperature threshold T th and the voltage of battery 1 is V b is the voltage threshold V th Even in the above cases, the detected output current I c is a given current threshold I cc If less than this, the gate resistance R g is the low-resistance second gate resistor R g2 (second value).

[0069] In this embodiment, the controller 10 controls the voltage V b , current command value I a , and the predicted temperature of the power module 22, the speed switching signal S sw The gate driver IC 23a (drive circuit 23) generates a speed switching signal S sw With reference to the above, the gate resistance R g However, this is not necessarily limited to this. That is, the voltage V of the battery 1 is set b , current command value I a (or the output current I c ), and the temperature of the power module 22. g For example, a high-resistance first gate resistor R g1 A circuit in which the second gate resistor R g2 Alternatively, two circuits may be provided, one of which can be selected, and the controller 10 may select one of the circuits by a switching operation using a hardware switch.

[0070] In addition, as in the present embodiment, the cooling water temperature T w It is preferable to predict the temperature of the power module 22 based on the temperature detected by the temperature sensor, but this is not necessarily limited to this. For example, a temperature sensor or the like may be provided in the power module 22, and the temperature of the power module 22 may be predicted based on the temperature detected by the temperature sensor.

[0071] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments. [Explanation of symbols]

[0072] 1: battery, 11: voltage sensor, 2: inverter, 22: power module, 220: power semiconductor element section, 221: switching element, 23: drive circuit, 24: cooler, 25: cooling water temperature sensor, 3: motor, 10: controller, 100: motor control system

Claims

1. A method for controlling an inverter for driving a motor having a power module, comprising: Predicting a temperature of the power module; Detecting the voltage of a battery supplying power to the motor; Calculating a command value for a current to be supplied to the inverter, or detecting an output current of the power module; setting a gate resistance of the power module to either a first value or a second value having a resistance value lower than the first value, based on a temperature of the power module, a voltage of the battery, and the current command value or an output current of the power module; Inverter control method.

2. 2. A method for controlling an inverter according to claim 1, comprising the steps of: A temperature of cooling water for cooling the power module is predicted as a temperature of the power module. Inverter control method.

3. 3. A method for controlling an inverter according to claim 2, comprising the steps of: When the coolant temperature is lower than a predetermined value and the voltage of the battery is lower than a predetermined voltage value, the gate resistance is set to the second value. Inverter control method.

4. 4. A method for controlling an inverter according to claim 3, comprising the steps of: When the cooling water temperature is less than a predetermined value, and the voltage of the battery is equal to or greater than the predetermined voltage value, and the current command value is less than a predetermined value or the output current of the power module is less than a predetermined current value, the gate resistance is set to the second value. Inverter control method.

5. 4. A method for controlling an inverter according to claim 3, comprising the steps of: The current command value is calculated at a predetermined calculation period, set the gate resistance to the second value when the cooling water temperature is less than a predetermined value, and the voltage of the battery is equal to or greater than the predetermined voltage value, and a value obtained by adding a current command value to a maximum current increase value, which is a maximum value of a current that can be increased due to a change in the motor rotation speed within the predetermined calculation period, is less than the predetermined value, or a value obtained by adding the maximum current increase value to an output current of the power module is less than the predetermined current value; Inverter control method.

6. 6. A method for controlling an inverter according to claim 5, comprising the steps of: The inverter is mounted on a vehicle, predicting a maximum change in the number of rotations of the motor within the predetermined calculation period based on an acceleration resistance of the vehicle; a value of the current increased due to the predicted maximum change in the motor rotation speed is set as the maximum current increase value; Inverter control method.

7. A method for controlling an inverter according to claim 4, comprising the steps of: when determining whether the cooling water temperature is less than a predetermined value, whether the voltage of the battery is equal to or greater than the predetermined voltage value, whether the current command value is less than a predetermined value, or whether the output current of the power module is less than a predetermined current value, a hysteresis is set for the cooling water temperature, the voltage of the battery and the current command value, or the output current of the power module; a hysteresis threshold value of the battery voltage is set to a value equal to or greater than a maximum value of voltage fluctuation that can occur at a maximum power input / output to / from the battery, or is set to a maximum value of voltage fluctuation that can occur at the predetermined voltage value before determining whether the battery voltage is equal to or greater than the predetermined voltage value. Inverter control method.

8. A method for controlling an inverter according to any one of claims 1 to 7, comprising the steps of: When starting up the inverter, the gate resistance is always set to the first value. Inverter control method.

9. A control device for an inverter for driving a motor having a power module, A means for detecting the temperature of the power module; means for detecting the voltage of a battery supplying power to the motor; A means for calculating a command value of a current supplied to the inverter or a means for detecting an output current of the power module; a controller that sets a gate resistance of the power module to either a first value or a second value having a resistance value lower than the first value; the controller sets a gate resistance of the power module based on a temperature of the power module, a voltage of the battery, and the current command value or an output current of the power module. Inverter control device.

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